FLIGHT TRACKER: Is your flight on time? . More than 635 flights were grounded before the end of Monday and more were likely as airlines tried to restart their operations.

Travelers scheduled to fly through airports in the northeastern US and Chicago O'Hare on United Airlines today can rebook without fee (and any difference in fare will be waived) for new flights departing through March 19 from the northeastern USA and March 17 from Chicago.

According to the airport's website, three scheduled arrivals from Chicago on Monday were canceled while a flight from New Hampshire was delayed.

The stunning numbers tell the story - 1,907 flights delayed in the USA on Tuesday as of 7:30 p.m., and a whopping 6,195 flights canceled.

Hundreds of flights were canceled in the Washington D.C. area because of Winter Storm Stella. The state agency, which runs Logan, said it would work throughout the day to clear snow from runways and would keep the airfield open "unless conditions make snow removal operations unsafe". Other airlines were considering similar moves. "I can tell you what flights to ask for or grab them myself with the airline, and then when you get up there, they'll see it's already been done". They're also experiencing a number of delays but anticipate flight schedules will return to normal later on Wednesday. The weather won't be warming up through the week so delays and cancellations could extend into early Wednesday.

The cancellations were prompted by National Weather Service forecasts on Monday of up to 2 feet (60 cm) of snow in some parts of the Northeast.